Personally though, charity in cash only does so much these days from the average American.
Bad examples include paying off non-profit organization debt where if any extra cash exists after a period of time, it just goes towards raises, which is not a bad thing, but the business models may not match that of efficient planning. Then again, the same can be argued about tax cuts from large corporations that get ahead and put non-profit organizations out of business/operation(s).
A good example would be, donating money to disaster relief groups that specialize in feeding the hungry around the world. Specifically, the money could go into the machinary that packages canned foods and the engineers part time volunteers or modestly paid.
Plus, there is the whole argument of government assisted research programs. Does any more of our tax dollars matter if one agency is being funded $1 million, vs. multiple mistakes that are never realized until a weapons company decides to give some money back and is somehow leaked into the media - for example, ATK and its $100 million dollar return to the US government?
I say if you got the time, money and energy, be the guest. But your invitation will run dry when the image alone for the people that run your money with their name(s) isn't in your mail box, with or without a tax cut. Let DARPA, 3M and the Universities talk it out, we can just pay taxes and listen to war stories.